Experimental And Simulation Research On The Transport And Diffusion Law Of Point Source Pollution In Water Supply Pipeline

As an important infrastructure,the urban water supply pipelines provide a key guarantee for social and economic development as well as people’s entertainment life.However,at present,there are many prominent problems in the safety of urban water supply in our country,and there are frequent incidents of pipeline leakage and secondary pollution.When the pipeline damage and low pressure events occur,the pollutants outside the pipeline may enter the pipe network through the leakage location,and then pollute the city’s water supply,causing the decline of water quality,posing a global risk,and posing a serious threat to the life and health of the public.Due to the complex structure and wide distribution of the pipeline network,it is impossible to achieve all-weather monitoring of the urban water supply network in the whole region.Once a secondary pollution event occurs in the water supply network,it is difficult to quickly determine the location of the pipeline damage and take effective countermeasures.With the development of computer performance,numerical simulation has become an important means of studying fluid dynamics.Based on a large number of previous studies,this study used numerical simulation and model tests to discuss in detail the problem of point source pollution of pollutants in water supply pipelines.Numerical simulation is used as the main means to study the diffusion of point source pollutants in a single pipeline,and model tests are used to verify the correctness of numerical model.In this study,five variables including main pipe flowrate,main pipe diameter,mixing ratio,salt solution incident angle,and salt solution density were selected to study the pollutant diffusion process in combination with the characteristics of cross-section pollution phase distribution of the pipeline.In order to facilitate quantitative analysis,the "effective mixing length" is defined to represent the distance from the inlet of the salt solution to the uniform position of the solution.After analyzing various influencing factors,it is found that the value of effective mixing length increases with the increase of main pipe flowrate and main pipe diameter,but decreases with the increase of mixing ratio and salt solution density,and the main pipe diameter has the greatest influence.On the other hand,there is no significant relationship between the incident angle of the salt solution and the effective mixing length.The dimensional analysis method is used to derive the effective mixing length calculation formula according to the simulation calculation data,which can be used to predict the diffusion of pollutants in a single pipeline.On the basis of the study of point source pollution in a single pipeline,the problem of point source pollution diffusion of pollutants in a simple pipeline network is further studied.In the study,the main pipe flowrate,the diameter of branch pipe,the flowrate of branch pipe,the flowrate of salt solution and the density of salt solution were selected as five variables,and the working conditions were set by the orthogonal test method.“Effective mixing length” is also defined for quantitative analysis,and the relationship between each variable and the effective mixing length is explored through the range analysis method and the analysis of variance method.The results show that the significance of each influencing factor on the effective mixing length in descending order is branch pipe flowrate,main pipe flowrate,salt solution flowrate,branch pipe diameter and salt solution density.The effective mixing length of the solution decreases with the increase of the main pipe flowrate,salt solution flowrate and salt solution density,as well as increases with the increase of the branch pipe flowrate.In addition,there is no significant change relationship between the branch pipe diameter and the effective mixing length under the conditions of this test.The influence of five variables on the effective mixing length was analyzed by the dimensional analysis method,and a fitting formula with a higher fitting degree was obtained.In this paper,by means of numerical simulation and model test,in-depth research and comparative analysis on the diffusion of point source pollution in single pipeline and simple pipeline network was conducted,which provides theoretical support for practical engineering and offers a certain reference for in-depth research on secondary pollution of the water supply pipeline network.